There is an increasing awareness of the importance of vesicular membranes in the controlled storage, transport and release of internally confined neurotransmitters or lytic enzymes. In view of increased interest, there are several questions relating to the basic structure and function of vesicular membranes which should be answered: What controls fusion and release of vesicle contents at particular membrane sites and at particular points in time? What mechanisms lead to concentration of solutes within the membraneous structures? And what factors provide for long term stability under conditions which would seemingly generate high solute concentration gradients and osmotic pressures? Overall objectives of this project have been to provide partial answers to these questions through in depth studies of model and natural systems using primarily nuclear magnetic resonance techniques. Specific goals for this year are fourfold. First, a continued structural characterization of the phosphatidic acid (PA)-phosphatidylcholine (PC)- 2 plus Ca vesicle system will be pursued. Solids nmr techniques for observing 31P and 113Cd in the analogous PA-Cd system will be employed to structurally characterize the cation -anionic lipid complex as well as identify conditions under which phases other than lamellar ones may be formed. Second, other anionic lipid systems such as the phosphatidylinositol system will be examined for fusion properties. Third, nmr methods for studying permeation will be extended to small biologically relevant molecules such as serotonin. And fourth, a detailed analysis of lipid motion in vesicles will be undertaken using coupled relaxation techiques.